After the walled garden coming to the desktop operating system world, we're currently witnessing another potential nail in the coffin of the relatively open world of desktop and laptop computing. Microsoft has revealed [.pptx] that as part of its Windows 8 logo program, OEMs must implement UEFI secure boot. This could potentially complicate the installation of other operating systems, like Windows 7, XP, and Linux.

Why after Microsoft? It will be OEMs who implement this feature. If they are too lazy to allow disabling or they void warranty if user does then it is hardly MS fault.

If MS says there can´t be an option to disable this then it would leave OEMs without much choice.
Remember, MS did this when it forbid OEMs to bundle 3rd party web browsers; it was a condition to retain OEM status.